The project involves examination of the effects of exposure to H2SO4 mist (approximately 0.3 Mum) for 1 hr/day, 5 days/week for up to 52 weeks upon the mucociliary clearance system, using rabbits as the animal model. Clearance during the period of exposure and for 26 weeks after will be monitored by serial, external measurements of an inhaled, radioactively tagged, tracer aerosol. Airway resistance will also be examined during the exposure period. At four time intervals during the 52 weeks exposure and at two time intervals during the follow-up period, groups of rabbits will be sacrificed and quantitative histological analysis of the epithelium will be performed. The study will provide information on the quantitative and temporal changes in mucociliary clearance and airway histology as these may relate to the pathogenesis of chronic bronchitis due to H2SO4 exposures.